Debug and step through addon?
You can do this with Free &amp; Open Source software, using Eclipse and PyDev. 


Download &amp; install Eclipse from https://eclipse.org/downloads/
Follow PyDev installation manual http://www.pydev.org/manual_101_install.html
Install my remote debugging add-on from Github
Configure it in the addon preferences for /home/sybren/.p2/pool/plugins/org.python.pydev_5.3.0.201610121612/pysrc/pydevd.py (adjust for your system)
Start a debug server in PyDev
Press Space in the 3D view and search for "pydev", then choose the operator to connect to the PyDev debugger.


You can see me explaining the steps in my Blender Conference 2016 talk Develop add-ons like a pro.